OneLinerBase64.scala

object Base64 {
  def main(args: Array[String]): Unit = {
    val str = "input here"
    val result = str.getBytes
      .flatMap(b => (0 until 8).map(n => (b >> (7 - n)) & 1))
      .grouped(6)
      .map(b => b.indices.map(n => b(n) << (5 - n)).sum)
      .map("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"(_))
      .grouped(4)
      .flatMap(_.padTo(4, '='))
      .mkString

    println(result)
  }
}